How to optimise data centre energy efficiency with sensor selection

Choosing the right HVAC sensors for your data centre can have a significant impact on energy efficiency and power usage effectiveness (PUE). While sensor investment costs are relatively small, the impact on your energy use can be disproportionately large. The right sensor solution may depend on your monitoring needs

Words by Anu Kätkä, Vaisala

Small investment, big impact

The number of data centres is growing, with over seven million worldwide in 2022 and a 10 per cent annual industry growth rate. Data centres are incredibly energy intensive, accounting for more than 1 per cent of global energy consumption – and, with increasing computing power needed, this figure is expected to increase. Therefore, the need to lower data centre power consumption and improve sustainability is increasingly urgent. HVAC sensors have a significant role to play in addressing this challenge.

Getting the balance right

Power usage effectiveness (PUE) is among the important figures to monitor if you’re looking to increase energy efficiency. It is defined as the ratio of the total energy used in a data centre and the energy used solely by IT. Ideally, PUE would be close to 1.0, which would mean that all energy is spent on IT and almost nothing on anything else. To do this you need to minimise the consumption of supporting infrastructure, like cooling or power distribution. Historically, the typical PUE in a conventional data centre has been around 2.0, whereas big hyperscale data centres have achieved a PUE below 1.2 or even less. In 2020 the global average PUE was 1.6, which would mean that on average 40 per cent of energy was used for non-IT consumption.

As PUE is a ratio, it is a good idea to look at total consumption as well. It is also important to consider how the electricity is produced and whether renewable sources can be used, how the excess heat could be utilised, and how to reduce other environmental impacts like minimising the amount of water used for cooling. In any case, one of the key drivers is minimising energy consumption. The numbers are big: 1 per cent of global energy consumed by data centres is a significant share, and even up to 40 per cent of that energy is used for cooling and air conditioning. Fortunately, that figure can be improved with accurate measurements.

It all starts with a sensor

Sensors and transmitters have an essential role in building automation and building management systems (BMS). Sensors are crucially important, as everything the system does is based on measurements. The BMS monitors prevailing indoor and outdoor conditions through parameters such as temperature and humidity and performs controls. Precise indoor conditions can be accurately maintained only through accurate measurements, which you can fully trust throughout the life cycle of the building.

You might need additional sensors when you already have a BMS in place and you’d like to verify, monitor, and optimise your building systems – in this case, you will benefit from a separate environmental monitoring system to monitor, map, and show trends. You may also want to report to third parties who should not access your BMS, for example, to show that you have fulfilled service level requirements.

High-quality sensors allow you to optimise your indoor conditions and the energy efficiency of your site, thereby directly influencing your PUE. You will have more control of the conditions in your data centre, helping you to achieve better indoor air quality, and you will improve your data centre’s overall sustainability.

Choosing a sensor solution

There are several important criteria to consider when choosing a sensor solution, including reliability, stability, accuracy and the needs of different spaces in your data centre. Stability is the most important criterion; it means your sensor is accurate and reliable even in demanding environments, both now and in the long term. When you are buying sensors, the data sheets may state similar accuracies. It is easy to compare these numbers, but harder to understand and verify how accurate a sensor will be after one year, or a few years. All sensors drift, but some drift a lot or quickly, while others have good stability with minimal drifting, maintaining measurement accuracy for years. Therefore, the stability of sensors should be the most important criterion because it influences performance over a long time and is reflected in calibration and maintenance requirements.

Despite good stability, high-quality instruments are also easy to maintain, calibrate, adjust and fine-tune. Having convenient tools available for verifying and maintaining the sensors and transmitters is about reliability and peace of mind throughout the life cycle. When you have a high-quality, reliable sensor that you can trust, you have assets to optimise both your indoor environment and your energy use.

A sophisticated transmitter is also capable of providing calculated humidity parameters straight from the transmitter, for reliability and ease of system commissioning. Other factors to consider include modularity, exchangeable probes and convenience –installation and commissioning should be flexible, while calibration and maintenance should be as easy as possible.

Optimised energy efficiency and lifetime value

HVAC measurements have a critical role in control and monitoring, and measurement quality matters when it comes to your PUE. Reliability and stability mean accuracy in the long term, which should be taken into consideration already upon instrument selection. In a nutshell, investing in high-quality measurement instruments just makes sense. It is a minor investment in the context of a data centre project, but the value that you get from high-quality measurements is so much bigger. You can trust the measurement, now and in the future, helping you to reach the best possible PUE and a sustainability boost.

For close to a century, Vaisala has measured the slightest shifts in environments, even in the harshest conditions. Our instruments and intelligence are used where it matters the most: from the world’s largest data centres to leading medical laboratories, from the frozen Arctic to the fierce hearts of hurricanes – and even on the barren surface of Mars. vaisala.com